1. Field of the Invention
This invention relates to a highly flexible instrument that is particularly adaptable for use as an endodontic instrument, most particularly, an endodontic file for use by practitioners in removing the pulpal material from an exposed root of a tooth and for shaping the root canal to receive filler material, usually gutta-percha. One of the most significant advancements in dentistry in recent years has been improved treatment of abscessed teeth. In the past a tooth, once abscessed, was usually pulled as the only remedy for removing the intense pain usually created when a tooth is abscessed. By "abscessed" usually means that the root canal of the tooth becomes infected and the infection causes pressure on the tooth and the nerve endings associated therewith that result in sometimes almost unbearable pain. With the advent of endodontics the drastic measure of extracting a tooth that has become abscessed has been eliminated.
The first step in the endodontic treatment of an abscessed tooth is to drill an opening in the crown of the tooth to provide access to the root canal. Once the root canal adjacent the crown is exposed, the practitioner then must thoroughly clean the root canal of pulpal material since if the pulpal material is not thoroughly and carefully removed it can be the source of continued infection within the interior of the tooth. Not only is it necessary that the pulpal material be clean but the root canal usually must be shaped in such a way as to permit careful filling of the root canal with a filler material. While other types of filler materials have been provided still at the present time the most common filler is a paste-like material referred to as "gutta-percha." If the canal is not properly cleaned and shaped the step of filling with gutta-percha may leave void areas that invite the introduction into the root canal of organic matter that can be followed by bacterial action. For these reasons much of the effort by a practitioner to successfully accomplish the endodontic treatment of an abscessed tooth is the cleaning and shaping of the root canal and these steps are accomplished utilizing small diameter tapered files that are inserted by the practitioner through the exposed crown area into the root canal. The canal must be cleaned from the crownal area advancing to the root apex. Root canals naturally occur in a tapered configuration, that is the cross-sectional diameter of the root canal is usually greater near the crown of the tooth and usually is at a minimum at the apex of the tooth, that is the distal end of the root of the tooth. While the root canal is naturally tapered it is not tapered symmetrically and the canal can have inclusions in intermediate portions between the apex and the crown area that interfere with the passage of filler material. Therefore the crown must be shaped to remove unnecessary intrusions into the canal and to improve the chances that the practitioner can successfully fill the root canal with filler material.
Files are usually provided with a small cylindrical plastic handle portion by which the practitioner manually manipulates the files. By "manipulation" means inserting a file into a canal and reciprocating it to file away intrusions and at the same time to gather pulpal material and the results of the scraping action. Typically the practitioner inserts a file to the point of resistance and then rotates and reciprocates the file to engage spiral scraping edges with the canal wall and then extract the file to remove pulpal material and matter scraped from the wall. This procedure is repeated as necessary to clean the entire length of the canal. In the cleaning process the practitioner usually starts with a file of a small diameter and then, as progress is made in cleaning the canal, larger diameter files are employed until the root canal is shaped and cleaned to the apex. Accordingly, endodontic files usually come in sets of standard tapers and varying from small to larger diameters.
Root canals are characteristically not straight. Some root canals curve more than others but few are perfectly straight from the crown to the apex. Therefore it is important that files be flexible so as to be able to follow the natural curvature of the root canal as it is cleaned and shaped from the tooth crown to the tooth apex. If a file is too stiff it can result in the file protruding through a side wall of the root which can introduce an area of infection into the tooth and therefore is highly undesirable. Further, if the file is stiff it is less successful in cleaning the entire area of a canal since the stiffness will cause the file to be deflected drastically to one side of a curve in a canal leaving a portion of the wall that defines the inside of the curve unexposed to the action of the file for cleaning and shaping. Therefore, a high degree of flexibility is a very desirable characteristic of an endodontic file.
In addition, the strength of a file is very important. In the process of reciprocating and rotating a file in a tooth it is possible for the file to break off leaving a broken part in the tooth. This creates a serious problem for the practitioner. Accordingly, it has long been a desire of the dental profession to have available dental files that are highly flexible and yet strong to resist separation as a result of a torsional twist or pulling action as a file is manipulated within a root canal. The present invention provides away of substantially increasing the flexibility of dental files while at the same time increasing resistance against torsional or elongational separation.
2. Prior Art
For additional background information on the construction and use of highly flexible instruments, such as endodontic files, reference can be had to the following previously issued United States patents including the references cited in each of them.
U.S. Pat. No. INVENTOR TITLE 4,934,934 Arpaio, Jr. et al. Dental File/Reamer Instrument 5,106,298 Heath et al. Endodontic Dental Instrument 5,628,674 Heath et al. Endodontic Instrument